JPH0236172B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an infrared detection device for detecting specific conditions such as fire.

(b) Prior Art FIG. 1 shows an infrared detection section 1 of a conventional infrared detection device for detecting fire conditions.

Reference numeral 2 denotes a pyroelectric infrared detector made of a pyroelectric material such as lithium tantalate (LiTaO ₃ ) single crystal, which generates a charge according to the amount of change in incident infrared rays, and is polarized in the direction of arrow a. 3 and 4 are front and back electrodes formed on the front and back surfaces of the infrared detector 2 with nichrome vapor deposited films, respectively; 5 is a metal support made of copper, phosphor bronze, etc.; With the back electrode 4 facing the top surface of the support base 5,
The infrared detector 2 is fixed with a conductive adhesive 6 such as silver paste. Reference numeral 7 denotes an impedance conversion circuit with a low resistance on the output side connected to the infrared detector 2, 8 an alumina substrate on which the circuit is arranged, 9 a storage body consisting of a metal cap 10 and a header 11; The support stand 5 and the substrate 8 are fixed on the header 11.
Reference numeral 12 denotes a ground terminal directly implanted in the header 11, and this terminal is electrically connected to the back electrode 4 via the support base 5 and adhesive 6. Lead terminals 13 and 14 are respectively implanted in the header 11 via an insulating material, and both terminals are connected to the impedance conversion circuit 7.

15 is an opening formed in the cap 10 to allow infrared rays to enter the infrared detector 2 from the surface electrode 3 side; 16 is made of silicon or germanium that transmits infrared rays having a wavelength of 2 to 15 μm; and 16 closes the opening 15. The infrared filter 17 is a narrow band infrared filter that is formed on the inner surface of the filter and transmits infrared rays of a specific wavelength based on a specific temperature, that is, infrared rays with a wavelength of 0.8 to 7 μm, which increases when the temperature is high due to a fire. It has a multilayered structure of high refractive index materials such as lead (PbTe) and low refractive index materials such as zinc sulfide (ZnS).

FIG. 2 shows the circuit of the detection unit 1, and the impedance conversion circuit 7 includes a high input resistance 18 of 10 ¹⁰ to 10 ¹¹ Ω, an N-channel FET (field effect transistor) 19, and an output resistance 20 of about 10 KΩ. It is configured.

Therefore, normally at room temperature, most of the infrared rays that exist at this time are infrared rays with wavelengths other than 0.8 to 7 μm, and such infrared rays pass through the infrared filter 16 but do not pass through the narrowband infrared filter 17. .

In such a state, if a fire occurs in the detection range of the detection unit 1, the detection range becomes high temperature. Then, infrared rays with a specific wavelength of 0.8 to 7 μm, which hardly exist at room temperature, suddenly increase, and in this case, the infrared rays pass through the infrared filter 16 and the narrow band infrared filter 17 and enter the infrared detector 2. When such an incident occurs, the amount of infrared rays incident on the detection body 2 changes rapidly, and a positive signal is generated on the surface electrode 3 based on the polarization direction of arrow a, and the infrared rays are detected from the lead terminal 14 of the detection unit 1. signal is output,
Therefore, the occurrence of a fire is detected.

However, the detection section 1 is susceptible to noise and tends to output an infrared detection signal as described above even when no fire has occurred, resulting in extremely low reliability.

(c) Purpose The present invention aims to significantly improve the reliability of the infrared detection device by prohibiting the infrared detection device from generating a predetermined signal for fire detection, for example, even if noise occurs in the infrared detection section. It is something to do.

(D) Structure In order to achieve the above object, the present invention includes an infrared detection section that detects infrared rays of a specific wavelength based on a specific temperature from a detection range, and an ambient temperature detection section that outputs a signal based on the temperature change gradient of the ambient temperature. a level detection unit that detects whether the output signal of the ambient temperature detection unit has reached a predetermined level; the infrared detection unit detects the infrared rays of the specific wavelength; It is comprised of a signal output section that outputs a predetermined signal when detected.

(E) Embodiments Hereinafter, infrared detection devices according to embodiments of the present invention will be described in detail. Incidentally, the same parts as in the conventional example are denoted by the same reference numerals, and the explanation thereof will be omitted.

In FIG. 3, 21 is an infrared detection unit that detects infrared rays of a specific wavelength based on a specific temperature from a detection range, and 22 is arranged adjacent to the detection unit and outputs a signal based on the temperature change gradient of the ambient temperature. This is an ambient temperature detection section. The ambient temperature detection section is almost similar to the infrared detection section 21 described above, and includes a pyroelectric infrared detection body 2' that responds to changes in ambient temperature, front and back electrodes 3',
4', a metal support 5', a conductive adhesive 6', and a storage body 9. However, in the ambient temperature detecting section 22, the infrared detecting body 2' is
The cap 10 in front of the detector 2' is not provided with an opening to prevent external infrared rays from entering the detector 2'.

FIG. 4 shows a circuit including the infrared detecting section 21 and the ambient temperature detecting section 22.
On the side, an impedance conversion circuit 7' is provided as a level detection section, and this circuit, similar to that of the infrared detection section 21, has a high input resistance 18' of 10 ¹⁰ to 10 ¹¹ Ω, an N-channel FET 19', and an N-channel FET 19'. It consists of an output resistor 20' of 10KΩ. 23 is connected to both the detection units 21 and 22, and the detection units 21 and 22 are
A control section 24 serves as a signal output section that outputs a predetermined signal K based on the output of the control section.
This is a notification unit that issues a fire alarm based on the following.

Thus, when a fire occurs within the detection range of the infrared detection section 21, the detection range becomes high temperature. Then, as described above, the amount of infrared rays incident on the detection body 2 with a wavelength of 0.8 to 7 μm increases rapidly, a positive signal is generated on the surface electrode 3, and the lead terminal 1 of the infrared detection section 21
4 outputs an infrared detection signal.

Furthermore, in the ambient temperature detection sensor 22, the ambient temperature rises rapidly at a rate of 1.5°C or more per minute due to the high temperature during the fire, and in this case, the infrared detector 2' is polarized in the direction of arrow b. Therefore, a negative signal is generated at the surface electrode 3'. Such a negative signal is extremely large due to the rapid temperature rise change, and the gate potential of the FET 19' in the impedance conversion circuit 7' serving as the next stage level detection section swings significantly to the negative side beyond a predetermined level, and at this time, depletion occurs at the gate. Due to the expansion of the layer, the source and drain are cut off, so that the source output of the FET 19' decreases from a positive predetermined value and reaches a steady state of 0 volts. Then,
This means that the impedance conversion circuit 7' has detected a predetermined level signal by outputting 0 volts.

Note that the above-mentioned rapid increase in ambient temperature also affects the detection object 2 of the infrared detection section 21, but in this case, the gate potential of the FET 19 swings significantly to the positive side (so that the depletion layer disappears), and the infrared detection The signal just gets louder.

The control unit 23 receives an infrared detection signal which the infrared detection unit 21 outputs by detecting infrared rays with a wavelength of 0.8 to 7 μm, and a 0 volt signal which the impedance conversion circuit 7' detects and outputs a predetermined level signal at this time. A signal is input. Here, the control unit 23 is configured to output the predetermined signal K when both the infrared detection signal and the 0 volt signal are input, and therefore, in the above case, the notification unit 24 outputs the predetermined signal K when the signal K is applied. A fire alarm is issued to prevent the fire from occurring.

On the other hand, even when no fire occurs, the infrared detection section 21 may output an infrared detection signal as described above due to noise. However, in this case, the ambient temperature of the ambient temperature detecting section 22 does not rise because there is no fire, and as a result, no 0 volt signal is output from the impedance conversion circuit 7'.
Therefore, since the control section 23 only inputs the infrared detection signal and therefore does not output the signal K, the notification section 24 will not issue a fire alarm.

(e) Effects As is clear from the above description, according to the present invention, an infrared detection section detects infrared rays of a specific wavelength based on a specific temperature from a detection range, and outputs a signal based on a temperature change gradient of the ambient temperature. an ambient temperature detection section that detects whether the output signal of the ambient temperature detection section has reached a predetermined level, a level detection section that detects whether the output signal of the ambient temperature detection section has reached a predetermined level; Since it is equipped with a signal output section that outputs a predetermined signal when a predetermined level signal is detected, for example, a fire alarm will not be issued by mistake due to noise to the infrared detection section, making it an extremely reliable infrared detection device. Can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a conventional device, FIG. 2 is a circuit diagram of the main part, FIG. 3 is a sectional view of a main part of the device of the present invention, and FIG. 4 is a circuit diagram of the same. 21... Infrared detection section, 22... Ambient temperature detection section, 7'... Impedance conversion circuit, 23...
control section.

Claims (1)

[Claims] 1. An infrared detection section that detects infrared rays of a specific wavelength based on a specific temperature from a detection range, an ambient temperature detection section that outputs a signal based on the temperature change gradient of the ambient temperature, and an output signal of the ambient temperature detection section that is at a predetermined level. a level detection section that detects whether or not the level has been reached; a signal output section that outputs a predetermined signal when the infrared detection section detects the infrared rays of the specific wavelength and the level detection section detects a predetermined level signal; An infrared detection device characterized by: